No, I still hadn't been there. Only route on Cvrsnica I am familiar with is the one from Masna luka to Plocno (actually, the next weekend I'm going - weather permitting - to climb Vran and day after Plocno) and I hope that Vilinac will come into the schedule soon enough. So many mountains, so little time. :)

The name is coming from middle age. Hajduci were kind of thieves at that time and they were hiding in mountains and hardly accessible areas. (Hajducka vrata, eng. Rebel's door)
I suppose this translation is not totally correct, but it is closest I found.
So I suppose these "door" is quite older than people usually think.
And most impressive is thing that they are naturaly shaped.